1. Field of the Invention
The present invention relates to a laser light source for implementing pulsed oscillation of laser light.
2. Related Background Art
A laser light source for implementing pulsed oscillation of laser light is provided with a laser cavity in which a laser medium for generating emitted light with supply of excitation energy is placed on a resonance path, a Q-switch device for modulating a cavity loss of the laser cavity, and an excitation device for continuously supplying the excitation energy to the laser medium.
This laser light source is configured as follows: while the cavity loss of the laser cavity is set at a large value by the Q-switch device, the population inversion of the laser medium is enhanced with supply of excitation energy by the excitation device; when the cavity loss of the laser cavity is then set to a smaller value by the Q-switch device, induced emission occurs in a short period of time in the laser medium placed on the resonance path of the laser cavity. This induced emission is outputted as laser light from the laser cavity to the outside.
Since such laser light sources are able to output pulsed laser light with a high peak power, they are commonly used in electronic and mechanical processing applications, medical laser knives, measurement applications such as measurement of length, and so on. For example, in the processing applications, the radiated laser light for processing is required to achieve the stability of output power of about 5% p-p. However, the conventional laser light sources do not always achieve satisfactory stability of pulse output.
Which is important between energy and power of pulsed laser light is dependent upon types of processing such as welding or cutting, and upon types of machined objects. As a general tendency, importance is attached to the energy of the pulsed laser light in cases of conventional thermal processing. In contrast to it, the power density (W/cm2) of pulsed laser light is also an important factor in processing applications requiring femtosecond pulses, e.g., ablation, and efficiency of absorption of pulsed laser light is drastically improved at the power density of over 1015 W/cm2.
Japanese Patent No. 3331726 and Japanese Patent Application Laid-Open No. 2001-332791 disclose the laser light sources intended for stabilizing the energy or power of output pulsed laser light. In the laser light sources disclosed in these documents, part of pulsed laser light outputted from the laser cavity to the outside is branched and extracted, and the power of the pulsed laser light branched and extracted is monitored. Then feedback control is performed so as to stabilize the energy or power of the output pulsed laser light, based on the result of monitoring.
However, the laser light sources adapted for feedback control as disclosed in the above-described Documents 1, 2 were not always satisfactory in terms of the energy or power of the output pulsed laser light.